The CT scan is one of the most important developments in medicine (and neurosurgery in particular) of the past fifty years. CT scan allows for the localization of lesions in the brain or spinal cord. It is particularly useful in determining if there is bleeding in the brain or bony destruction in the spinal column. For this test, you will be asked to lie on a bench while a series of special X-rays are taken. For a simple head CT, this can take less than thirty seconds. Scans of other body parts may take up to thirty minutes. Additionally, some tests require that intravenous contrast dye be administered. Patients with kidney problems, allergies to shellfish, or previous reactions to contrast dye should make certain that their physician is aware of these conditions prior to receiving contrast dye.